http://www.newscientist.com/article/mg21829131.900-space-oddity-putting-quantum-weirdness-into-orbit.html?page=3 23 April 2013 by Sophie Hebden Bibliography Visit her blog at sophiehebden.wordpress.com
The hope is that by doing the measurements we can bore more deeply into vexed questions of cause, effect and reality in the quantum world. Is a wave function a real object, and its collapse a process that happens in space and time? Or is it merely a mathematical shorthand for our state of knowledge of a quantum system, with the real action happening on a level we have not yet penetrated? Einstein favoured the second view, sparking a debate that continues to this day. "It's still very controversial, how to reconcile wave function collapse with our usual notions of reality and causality," says Rideout.
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Climbing out of the rabbit hole, we can ask the question, “Are we missing something?”
Climbing out of the rabbit hole, we can ask the question, “Are we missing something?”
Let us see if the two theories connect on the radius of
curvature, accounting for scale variance +/- VC differentials, at both velocity
and frequency scenarios. Prior to reviewing quantum and relativity in
the New Scientist article, I would suggest a recap of the simple but clearly
articulated definitions in the first post in this blog, along with the following
points we know. Contrasting outcomes, what you “see”, in the +/- VC frequency scenario
with a stationary object nearby, and one at +/- VC velocity differential should
reveal the full significance of the constant C.
- · The quantity C is the kinetic energy equivalent of the mass energy of matter. The quantity C is a degree of energy differential. We can define it as the maximum differential which can exist between two reference points in the factor which we call matter. We can also define it as the minimum differential which can exist between a reference point in matter, and one in energy. This is only true, however, when the reference point in matter is at the same energy level as the observer.
- · The natural laws are not absolute, but relative.
- · That is, the size and shape of the curve of one law is dependent upon the value and position of the others.
- · If a differential of energy equal to the quantity C exists between the observer and the point which he is observing, the natural laws will be suspended.
- · If the energy differential is in excess of the quantity C, the laws will appear to operate in reverse at that point.
- · The Bell device was designed to use high-speed counter-rotating components filled with specialized materials and energized by electromagnetic energy to induce “torsion” effects and thus control gravity and other significant effects.
- · We refer not only to the charges in the outer shell of the atom but to those within as well, and especially to the fact, not always realized, that the neutron possesses both a positive and a negative charge, although when united within the neutron they are not discernible as charges, but exist as energy which produces the gravitational field.”
- A Power Point Introductory Presentation http://www.relaxspa.net/TheRadiusOfCurvature12-28-10PPShow2003.pps
http://www.newscientist.com/article/mg21829131.900-space-oddity-putting-quantum-weirdness-into-orbit.html?page=3
by Sophie Hebden
What
happens when our two greatest theories of reality meet? Soon quantum theory and
relativity could be slugging it out above our heads
IT IS a meeting point, this
vast expanse of near-nothingness hundreds of kilometres above our planet's
surface. Here, Earth's gravity is too weak for atmospheric gases to linger, but
the absolute emptiness of outer space has not yet quite begun. Human activity
is ever-present. Satellites wink and blink, monitoring, directing,
communicating.
These
satellites too are a meeting point. Deep within their sensors and electronic
circuits, electrons and photons dance to the tune of our most fundamental
theory of nature's workings: quantum theory. Its
fuzzy uncertainties and instantaneous influences provide a peerless description
of matter on the smallest scales. But to predict how a satellite itself will
move – or any large body, from falling apples to stars, galaxies and the
universe itself – we must call on a very different mathematical construction:
the rigid, space-warping equations of Einstein's theory of gravity, general
relativity.
These two theories really
don't get along. In fact they are fundamentally, mutually antagonistic. So what
happens when one trespasses on the other's territory? To find out, there is
only one way to go. We must take our quantum experiments into relativity's
realm – that marginal zone far above our heads.
If we have as yet failed to
find a chink in the armour of quantum theory or relativity, it is not for want
of trying. The space-warping quirks of relativity that lead to deviations from
Newton's earlier theory of gravity only become obvious on very large scales,
but our passive observations of distant planets, stars and galaxies have yet to
deliver anything incompatible with Einstein's ideas. We can test quantum
theory's weirdness more directly here on Earth, with the same result – which
was much to Einstein's distaste.
Take
experiments performed by Anton Zeilinger of the University of Vienna, Austria, and his team over the past
few years, beaming photons of light great distances in the Canary Islands. In
quantum theory, particles such as photons exist as wave functions,
probabilistic entities depicted as being in all their possible quantum states
at once. When they are measured, however, they "collapse" into a
definite state. What's more, the effect known as entanglement allows the fates
of two or more particles to be intertwined. By measuring the state of one
particle, you can collapse the wave function of another, seemingly
instantaneously, however far away.
Einstein
was dismissive of this "spooky action at a distance", preferring to
think that some hidden, physical influence connected the measurements. Yet
working on moonless, still nights to beam one of an entangled pair of photons
144 kilometres between the islands of La Palma and Tenerife, Zeilinger and his
team observed just the correlated collapse in the photons' states that quantum
theory dictated (New
Scientist, 26 February 2011, p 36).
Such trickery is already in
practical use. An eavesdropper cannot listen in on information encoded in
entangled quantum states without collapsing them, thus revealing the
interception. Cryptographic keys written in photon polarisation states are now
used to encode and decode messages in small-scale fibre-optic networks set up
by government agencies, research labs and commercial companies worldwide.
This has its limits,
though. Beyond a hundred kilometres or so, absorption within fibre-optic cables
tends to disturb any quantum information transmitted along it, rendering it
useless. Unlike for classical information, we do not have any reliable way to
boost quantum signals along their route. If we want to be enjoying the fruits
of secure, global quantum communication any time soon, we will have to beam the
signals via satellite.
That gives a practical edge
to a very fundamental question. "We've seen entanglement work over
macroscopic distances, but is it going to work forever?" asks Giovanni
Amelino-Camelia, a theorist at the Sapienza University of Rome in Italy. And
there is good reason to believe that the sky might indeed be the limit.
Conflicting
clocks
Entanglement as we know it
on Earth relies on quantum theory's assumption that space and time form an impassive,
unchanging background against which events such as measurements simply take
place. Perform a measurement in one place, and observe a correlated effect in
another, and you can be reasonably sure the one influenced the other. But in
relativity's realm, space and time are, well, relative. Time appears to tick
more slowly and space to contract for objects moving at high speeds relative to
one another. The closer an object is to a large source of gravity, the slower
its clock will run.
Such effects are negligible
on Earth's surface, but GPS systems routinely correct for them as their signals
bounce to and from satellites. And they could mean, for example, that the order
in which things happen in quantum experiments is no longer so clear cut. How do
relativistic effects change things such as entanglement, if at all?
It is not
the first time we have posed that question, but previous proposals to answer it
have been frustrated. Zeilinger has been in discussions with the European Space
Agency since 2002 aboutputting
an entangled-photon source on the International Space Station so that he can fire them down to detectors on Earth. "Their
answer is not a no, but a not yet," he says. A proposal in 2010 for a
quantum link-up to a microsatellite sent into low Earth orbit by the Canadian
Space Agency was eventually passed over, although "the possibility of
doing fundamental science with the satellite remains", says one of the
scientists involved, David Rideout of the University of California, San Diego. Last year, NASA
organised a conference to bring its space scientists together with quantum
physicists, and there are "rumours" of its willingness to fund an
experiment, says Zeilinger – but nothing more than that.
Satellite
state
Enter the
new, muscular player in all things space: China. An erstwhile student of
Zeilinger's, Jian-Wei Pan of
the University of Science and Technology of China in Hefei, is now leading a
team developing the Quantum Science Satellite, the world's first dedicated
quantum space probe. Due to launch in 2016, it will have a sun-synchronous
orbit: it will pass over locations on Earth at the same time each day at an
altitude of 600 kilometres.
Zeilinger
is in on the project too. The first aim is to share a quantum cryptographic key
via satellite between the Chinese Academy of Sciences in Beijing and Zeilinger's
institute in Vienna. This will be used to decrypt a secure intercontinental
phone call between the two – if things pan out. "The pressure's going up,
we have a lot of challenges to overcome," says Yuao Chen of
the Chinese team. Collisions with air molecules that disrupt the photon beams
should be less of a problem than in the Canary Islands experiments: by going up
and down, the photons travel less distance in the thickest layers of the
atmosphere. Even so, only one of every million entangled particles transmitted
is expected to make it to the detector.
The real
problem is that the satellite will only be visible to the ground stations in
China and Europe for a few minutes at a time as it shoots overhead at 8
kilometres per second. It will require a sure aim to lock the laser beams to
the passing satellite. Pan and his team have been getting their eye in using a
hot air balloon to simulate the vibrations, random movements and changes in
altitude of a space platform, and a moving van with a rotating turntable to
model the satellite's rapid fly-by (arxiv.org/abs/1210.7556).
The Chinese team is also
investigating whether it is possible to make detectors that are sensitive
enough to pick up entangled photons during the day – a decisive step to making
a practical worldwide secure quantum communications network. "I find it
fascinating, having done fundamental research for so many years, that we are
moving closer to applications now," says Zeilinger. "It's a
completely new game."
One,
perhaps, with completely unknown rules. "We're not expecting entanglement
to break down," says Zeilinger. But at the very least we can expect some
ticklish questions. Beam a pair of entangled photons up to two satellites
moving at speed towards one another, and measure them concurrently from the
point of view of Earth, then to each of the two satellites the other's
measurement appears to have happened first (see diagram). So
which measurement caused the wave functions to collapse?
The hope is that by doing
the measurements we can find out, and so bore more deeply into vexed questions
of cause, effect and reality in the quantum world. Is a wave function a real
object, and its collapse a process that happens in space and time? Or is it
merely a mathematical shorthand for our state of knowledge of a quantum system,
with the real action happening on a level we have not yet penetrated? Einstein
favoured the second view, sparking a debate that continues to this day.
"It's still very controversial, how to reconcile wave function collapse
with our usual notions of reality and causality," says Rideout.
Others are
not so sure that entanglement won't just break down at some point. Calculations
published in February by Tim
Ralph of the
University of Queensland in Brisbane, Australia, and his colleagues suggest
that the relativistic time-stretching of a few hundred femtoseconds involved in
sending one of an entangled pair of photons from the ground to a satellite just
200 to 300 kilometres up could be enough to do just that. But the calculated
effect only really kicks in for short, well-defined photon pulses that are
themselves less than about 100 femtoseconds long. That should not be a problem
for the initial Chinese experiments, which will use a continuous beam, but it
is something to watch out for (Physical
Review Letters, vol 110, p 060501).
For a
dedicated test, Ivette Fuentes, a
quantum theorist based at the University of Nottingham in the UK, and her
colleagues propose analysing the entanglement between Bose-Einstein
condensates. These large collections of atoms, chilled to near absolute zero,
behave as one quantum system. The idea is to hold entangled condensates in two
separate satellites, and then kick one into a different orbit. Calculations
indicate that the acceleration needed for a change in orbital radius of just
400 metres would disturb a condensate enough to noticeably degrade its
entanglement. A typical satellite manoeuvre changes orbital radius by as much
as 60 kilometres – enough to completely disrupt the transmission of information
in a future quantum network (Physical
Review D, vol 85, p 061701).
"From a theoretical
point of view, we've shown that there are effects, but we need to confirm this
with experiment," says Fuentes. And to test effects in space, we need to
go to space: on Earth, we are limited to experiments in "drop towers"
where condensates fall a maximum of 100 metres or so.
Entanglement is not the
only quantum phenomenon we need to examine carefully in relativity's realm,
either. Interferometer experiments on Earth, in which single photons are pinged
along two paths of equal length, then made to combine at the other end, have
seemingly confirmed that quantum objects can be in two places at once. In
space, the idea would be to repeat the experiment along two different paths,
one straight up to a satellite and along to a second, and one along close to
Earth's surface and then up to the second satellite. The two photons will have
passed along paths identical in everything but the average strength of gravity
along them. What happens then?
Long-sought
prize
We don't know, but that is
exactly the point, says Ralph. "Something different might happen. It's
very important to do these sorts of experiments to see if they really behave
the way we expect them to." He has been discussing how such an experiment
might be made reality with researchers from the European and Canadian space
agencies, among others.
Quite
apart from their relevance to any future satellite quantum-information network,
deviations from what quantum theory or relativity predict could deliver a
long-sought prize: the first whiff of a
greater theory that might allow them to set aside their differences and unite.
Theorists are not short of suggestions in the form of grand constructs such as
string theory, but testing them was long believed beyond our technological
capabilities. "Quantum gravity research was a free-for-all, the best
theories were decided by a show of hands," says Amelino-Camelia.
In the
late 1990s, he was among the first to point out an observable effect that a
very large quantum experiment in space might just catch. Over distances of less
than about 10-35 metres, at the Planck scale, most
theories of quantum gravity predict that space-time no longer acts like a
smoothly flowing continuum, as Einstein's relativity would have it. This
bumpiness could have a slow cumulative effect on the polarisation of photons, randomly
knocking them slightly out of kilter.
If the most optimistic
models turn out to be right, we could see an effect by beaming polarised
photons from the ground to a satellite in a low Earth orbit. At the worst,
though, we would need to put a detector billions of light years away. "We
have to be prudently pessimistic: we are just opening a window; it will only
work if we are lucky," says Amelino-Camelia. Yet even a no could be a
significant result, allowing us to start ruling out those theories that predict
larger, albeit still small, effects.
But the possibility of one
of these experiments presenting evidence of anomalous effects provides all the
motivation he needs to take quantum tests into relativity's realm high above
us. "If we get a yes, it will resound in the history of physics
forever."
This article appeared in
print under the headline "Where worlds collide"
